Question: Simplify the following expression: $k = \dfrac{25m^2 - 20pm}{5pm + 5m} - \dfrac{20m^2}{5pm + 5m}$ You can assume $m,n,p \neq 0$.
Answer: Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{25m^2 - 20pm - (20m^2)}{5pm + 5m}$ $k = \dfrac{5m^2 - 20pm}{5pm + 5m}$ The numerator and denominator have a common factor of $5m$, so we can simplify $k = \dfrac{m - 4p}{p + 1}$